This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. ABSTRACT The incidence of type 2 diabetes in children has increased dramatically in the past decade. With earlier onset and thus longer duration of disease these children will have increased health care costs;they may also have more complications than someone diagnosed in middle age. There is little published experience on the best treatment to maintain normal glycemia and prevent complications in children with type 2 diabetes. This trial will determine which of 3 treatments is most effective in maintaining glycemic control. Although the trial will not be long enough to assess if there is a significant difference in complications between these 3 arms, surrogate markers associated with complications will be measured (e.g., lipid profile, C-reactive protein, microalbuminuria). This is a prospective, partially double-blinded, randomized clinical trial with 3 treatment arms: metformin alone, metformin plus intensive lifestyle treatment (behavior modification program). The primary endpoint is time to failure defined as hemoglobin A1c or =8% for 6 or more consecutive months. Subjects will be seen every 1 to 4 weeks during the 2-6 months of the runnin. After randomization, subjects will be seen every 2 months in the first year and every 3 months in subsequent years. In addition, subjects in the lifestyle arm will meet with a PAL (physical activity and nutrition leader) once a week for the first 6 months, every 2 weeks in the 2nd 6 months and monthly thereafter. Endpoint measurements will be done at randomization, 6 months, 24 months and end of study.